There are many methods for detecting urban water supply leaks, and the "Technical Regulations for Water Leakage Detection in Urban Water Supply Networks" (CJJ 159-2011) lists a total of 8 methods: flow rate method, pressure method, noise method, listening method, correlation analysis method, and other methods (ground penetrating radar method, surface temperature measurement method, gas tracking method).

The hydrogen tracing method is a simple, efficient, safe, and reliable way to detect water leakage.

Replace or dissolve a mixture of 5% hydrogen and 95% nitrogen, known as a "tracer gas," into the pressure testing medium (compressed air, water).The flammable limit of hydrogen is 5.7%, therefore, a mixture of 5% hydrogen and 95% nitrogen is a safe gas. This tracer gas is non-toxic, odorless, non corrosive, and non flammable, and is commonly used in industrial welding operations to protect stainless steel from oxidation.

Before using a hydrogen leak detector to detect pipeline leaks, it is necessary to determine the accurate direction of the pipeline. If it is a newly constructed pipeline, the direction is of course very clear, and there is no need for pipeline detectors to help locate it; If it is an old pipeline system, the direction may be unclear or the buried direction of the pipeline may not be marked on the ground. In this case, a pipeline detector must be used to determine the direction of the pipeline.

Detection steps of hydrogen tracer method:

1. Inject tracer gas

After the pressure test is completed and confirmed to have leaks, inject 5% hydrogen and 95% nitrogen into the pipeline. According to relevant regulations, the air pressure should generally reach above the working pressure, because pipeline leakage is related to pressure. It may not leak under a certain pressure, but there may be leakage beyond that pressure.

When injecting tracer gas into the pipeline system, use a hydrogen detector to hold a probe and first check for any air leaks around the injection equipment itself, such as flanges, valves, pressure gauges, etc.

2. Mark the direction of the pipeline

It is very important to accurately know the direction of the pipeline as tracer gases do not have significant lateral diffusion. If the pipeline direction is unclear, use a pipeline detector to mark the pipeline direction.

3. Use a hydrogen detector to detect tracer gases along the pipeline route

(1) Use a handcart probe for detection.

There is a dome shaped rubber pad under the handcart probe, which collects gas when in contact with the ground. The vacuum pump of the instrument draws the gas to the built-in sensor. The handcart can be pushed and moved at walking speed above the pipeline.

(2) Use ground probes (or bell shaped probes) for detection.

Handcarts are not suitable for environments with many obstacles or damp ground. In such cases, ground probes can be used to detect tracer gases.

4. Excavate the leaking area.

After repairing the hydrogen detector and detecting the leakage point, on-site excavation will be carried out. Use a handheld probe to accurately locate the leakage point on the exposed pipeline during excavation and repair it.

Selection of instruments and equipment:

The leakage situation of pipelines is very complex, with various forms ranging from micro leaks to large leaks. The buried medium and on-site environment of pipelines are also constantly changing, which requires high requirements for the selection of hydrogen gas detectors. Instruments with detection functions suitable for various situations must be used to fulfill this task.

Recently, Zechuanjun took the German Shuchi GM5 to the Tangshan site to determine the direction of the hydrogen tracer pipeline. Below are several on-site pictures.

The on-site operator is holding the handcart style tracer gas pipeline inspection instrument GM5.

GM5 is a multifunctional instrument that, when paired with an inspection cart, does not require drilling or excavating the covering soil during inspection. Simply push the instrument and walk above the gas pipeline to directly detect the leakage location of underground gas pipelines on the ground. It can detect various gases such as methane, propane, hydrogen, and carbon monoxide.

Due to its measurement range from 1ppm to 100vol.%, GM5 canSuitable for: gas detection, pipeline leak detection, monitoring explosion limits, gas leak location, inspection and inerting, tracer gas technology.

GM5 can accurately and reliably perform pipeline detectionThe task is to combine measurement technology with ease of use, making it an ideal tool for full-scale measurement of public gas supply pipelines.

For more gas detection equipment and solutions, please contact Zechuan Technology!